Method and apparatus for enabling multiple optical line termination devices to share a feeder fiber

ABSTRACT

A method and apparatus for enabling multiple optical line termination (OLT) devices to share a feeder fiber are disclosed. For example, the optical network comprises a plurality of optical line termination (OLT) devices, where each OLT device having a transceiver for sending and receiving optical signals. The optical network further comprises a wave division multiplexer (WDM) combiner, coupled to the plurality of OLT devices, for combining optical signals received from the plurality of OLT devices. The optical network further comprises an optical extender box comprising at least one hybrid SOA-Raman amplifier, wherein the optical extender box is coupled to the WDM combiner via a first standard single mode fiber section. Finally, the optical network further comprises at least one optical splitter coupled to the optical extender box via a second standard single mode fiber section.

The present application is related to U.S. patent application entitled“METHOD AND APPARATUS FOR PROVIDING PASSIVE OPTICAL NETWORKS WITHEXTENDED REACH AND/OR SPLIT”, Ser. No. 11/546,237 and U.S. patentapplication entitled “METHOD AND APPARATUS FOR ENABLING MULTIPLE PASSIVEOPTICAL NETWORKS TO SHARE ONE OR MORE SOURCES”, Ser. No. 11/564,245,where both applications are herein incorporated by reference and bothapplications are simultaneously filed on the same date with the presentapplication.

The present invention relates generally to communication networks and,more particularly, to a method and apparatus for enabling multipleoptical line termination devices to share a feeder fiber.

BACKGROUND OF THE INVENTION

A passive optical network typically comprises an Optical LineTermination (OLT) located at a service provider site, a splitter locatedbetween the service provider site and the plurality of customer sites,and a plurality of Optical Network Terminations (ONT), e.g., 32 ONTs,for serving the customers. The passive optical network has limitationsdue to signal level requirements of the transceiver components in theOLT and ONTs. For example, a typical passive optical network may limitthe distance between the OLT and the farthest ONT to be 20 km with an1:32 split ratio due to the attenuation of the optical signals. However,as service providers expand their network, serving more and morecustomers with the same network and being able to extend the reach ofthe passive optical network become more and more important. Providing apassive optical network for every 32 customers does not allow serviceproviders to reduce the cost of the network, i.e., there is minimalsharing of network resources. In order to reach more customers and moredistribution locations, deploying a new feeder fiber becomes necessary.However, the cost of fiber deployment is prohibitive.

Therefore, there is a need for a method and apparatus that enablesmultiple optical line termination devices to share a feeder fiber.

SUMMARY OF THE INVENTION

In one embodiment, the present invention discloses a method andapparatus for enabling multiple optical line termination (OLT) devicesto share a feeder fiber. For example, the optical network comprises aplurality of optical line termination (OLT) devices, where each OLTdevice having a transceiver for sending and receiving optical signals.The optical network further comprises a wave division multiplexer (WDM)combiner, coupled to the plurality of OLT devices, for combining opticalsignals received from the plurality of OLT devices. The optical networkfurther comprises an optical extender box comprising at least one hybridSOA-Raman amplifier, wherein the optical extender box is coupled to theWDM combiner via a first standard single mode fiber section. Finally,the optical network further comprises at least one optical splittercoupled to the optical extender box via a second standard single modefiber section.

BRIEF DESCRIPTION OF THE DRAWINGS

The teaching of the present invention can be readily understood byconsidering the following detailed description in conjunction with theaccompanying drawings, in which:

FIG. 1 illustrates an exemplary network of the current invention;

FIG. 2 illustrates an exemplary embodiment of a PON of the currentinvention;

FIG. 3 illustrates the optical extender box of the current invention;

FIG. 4 illustrates an exemplary embodiment with four PONs sharing acommon feeder;

FIG. 5 illustrates an exemplary embodiment for multiplying the number ofONTs served by a feeder fiber; and

FIG. 6 provides an exemplary network with PONs heavily sharing sources.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures.

DETAILED DESCRIPTION

The present invention broadly discloses a method and apparatus forproviding passive optical networks with extended reach and/or splittingratio. Although the present invention is discussed below in the contextof passive optical networks, the present invention is not so limited.Namely, the present invention can be applied to extend the reach ofother fiber optic networks such as long haul and access networks.

The current invention discloses various passive optical networks thatare based on the hybrid SOA-Raman amplifier. In one embodiment, thereach and/or splitting ratio of passive optical networks can be extendedusing a hybrid SOA-Raman amplifier. In another embodiment, multiplepassive optical networks may share a feeder fiber by using the opticalgain of a hybrid SOA-Raman amplifier. In yet another embodiment,multiple passive optical networks are enabled to share source signalsfor enhancement services via a hybrid SOA-Raman amplifier deployed at acentral office.

FIG. 1 illustrates an exemplary network 100 of the current invention.Customer endpoint devices 102-104 are connected to the serviceprovider's network 110 through a passive optical network 101 to receivevoice and data services. The Passive Optical Network (PON) is used todeliver optical fiber signals to the end user, e.g. fiber-to-the-homesystems, fiber-to-the-curb systems, etc.

FIG. 2 illustrates an exemplary embodiment of a PON 200 of the currentinvention. In describing the interactions of the different components inFIG. 2, those skilled in the art would realize that FIG. 2 may alsoserve as a flowchart for describing the methodology for increasing thedistance between the OLT and the ONTs and/or increasing the splittingratio such that more ONTs may be serviced by the same splitter.

PON 200 may comprise an Optical Line Termination (OLT) device 240located at a service provider's site 260 (e.g., at a central office), anoptical extender box 280 of the current invention, a passive opticalsplitter 245 located at a remote node 250 (e.g., located close to thecustomer end devices), and a number of Optical Network Termination (ONT)devices 201 ₁-201 ₆₄. In one embodiment, the central office 260 is partof the service provider's network. Depending on the location of theoptical fiber termination, the ONTs 201 ₁-201 ₆₄ may be located at thecustomer site, at the curb, and so on. The location of the ONTsdetermines whether the system is described as fiber-to-the-curb (FTTC),fiber-to-the-building (FTTB), fiber-to-the-home (FTTH),fiber-to-the-node (FUN), or in the most general terms, FTTx.

A transceiver located on the OLT 240 is connected to the passive opticalsplitter 245 via a feeder fiber (e.g., standard single mode fiber) 265and optical extender 280. The optical extender box 280 may be located ina remote node at an optimal distance for amplifying the optical signalsreceived from the OLT 240. The passive optical splitter 245 is connectedto the ONTs 201 ₁-201 ₆₄ via distribution fibers 270. The term “passive”refers to the fact that the device has no power requirements or activeelectronic parts. In one embodiment, identical optical signals aredistributed to all the ONTs. Note that the power of the optical signalreceived by an ONT is a small fraction of the optical power received bythe splitter. In one embodiment, a de-multiplexer is used within eachONT to limit the received optical bandwidth (or wavelength) to thedesired signal for each user. Due to the power margins of lasertransmitters and photo detectors used in the OLT and ONT transceivers,the maximum reach for a PON without the optical extender 280 of thecurrent invention is often limited. For example, for a PON with asplitting ratio of 1:32 and an optical signal transmission over singlemode optical fibers, the distance between the OLT and the farthest ONTis often limited to 20 km. However, the optical extender box 280 of thecurrent invention may amplify the optical signals such that the distancebetween the OLT and the farthest ONT may be increased to 60 km (e.g., 40km for a first standard single mode fiber section and 20 km for a secondstandard single mode fiber section deployed on either side of theoptical extender box) and the splitting ratio may be increased, e.g., to1:64.

In one embodiment, the wavelength plan for TDM traffic on passiveoptical networks is downstream transmission in the band of 1480-1500 nmwavelengths, and upstream transmission in the band of 1260-1360 nmwavelengths. However, as businesses and services expand delivering“multiple” services on fiber links as close as possible to the customersbecomes more and more important.

In one embodiment, the current invention enables the service provider tooptionally provide additional services using other wavelengths. Thus,the optical extender box 280 of the current invention may amplify notonly the regular TDM signal but also as many as three or four additionalCoarse Wavelength Division Multiplexing (CWDM) wavelengths. Theadditional wavelengths may be used to provide video and data services.For example, depending on economic and technical considerations, theCWDM wavelengths centered at 1510 nm, 1530 nm, and 1550 nm may be usedeach with a distinct downstream service, or a larger number of a DenseWave Division Multiplexing (DWDM) wavelengths may be used. Eachenhancement wavelength may carry a separate downstream service.

In one embodiment, the WDM combiner 281 located at the central office260 is used to combine the CWDM signals sourced by a plurality ofenhancement OLTs, e.g., video OLT 276, other enhancement service OLTs277 and 278, with the TDM signals coming from the PON OLT 240. Thecombined optical signal is then transmitted on feeder fiber 265 towardsthe optical extender box 280. For customers who subscribe to theenhanced data and video services, their ONT 201 ₆₄ includes a WDMsplitter 282 (de-multiplexer) that directs the enhancement wavelengthsand the standard PON wavelength signals to one or more distinct opticalreceivers for detecting the specific services. For example, if acustomer subscribed to a video service provided on a particular CWDMwavelength, the optional ONT 201 ₆₄ for said customer includes ade-multiplexer that separates the CWDM wavelength from the signal to bedirected to the regular TDM receiver. The WDM splitter 282 directs theenhancement wavelength (the CWDM wavelength being used for video) to adistinct optical receiver that detects the video service.

FIG. 3 illustrates the optical extender box 280 of the currentinvention. The wavelength diplexers 301 and 302 are used to separate andrecombine the downstream and upstream wavelengths. The wavelength planfor Time Division Multiplexed (TDM) traffic on passive optical networksis downstream transmission (e.g., towards customer) in the band of1480-1500 nm wavelengths, and upstream transmission (e.g., towardsservice provider) in the band of 1260-1360 nm wavelengths. The lower legor portion 310 contains a hybrid SOA-Raman amplifier for the downstreamsignals and the upper leg or portion 320 contains a hybrid SOA-Ramanamplifier for the upstream signals.

The hybrid SOA-Raman amplifier is a two-stage amplifier comprising aconventional semiconductor optical amplifier (SOA) followed (or precededdepending on the implementation) by a low-powered Raman amplifier stage.The combination of SOA gain and Raman gain results in an amplifier withhigh and flat gain. For each leg, the high gain is determined by thepeak gain of the SOA stage. Note that the gain of the SOA stagedecreases monotonically with increasing wavelength. The flatness of thegain is due to the gain of the Raman amplifier stage that comprises aRaman pump laser, a pump coupler, and a non-linear fiber. The gain ofthe Raman amplifier stage acts to compensate for the monotonic decreasein the gain of the SOA stage. The optical bandwidth of the hybridSOA-Raman amplifier may exceed 100 nm with a gain flatness ofapproximately 1 dB or better. Since the amplifier has a total bandwidthexceeding 100 nm, it is capable of amplifying the 1490 band (from 1480to 1500-nm) and enhancement wavelengths in the range 1500 to 1580 nm.The loss of any additional transmission fiber is assumed to be 0.4 dB/kmand the loss associated with each doubling of the splitting ratio isslightly more than 3 dB.

For example, in a system with 10 km of added fiber and a splitting ratiothat has been increased by a factor of 4 to 1:128 (doubled twice), theamplifier needs to have a gain of at least 10 dB (4 dB to overcome thefiber loss and 2×3 dB to overcome the additional splitting loss).Similarly, for a system with 40 km of additional fiber and 1:64 split,the gain of the hybrid amplifier needs to be at least 19 dB. Adownstream gain of 20 dB is therefore large enough to compensate themaximum loss of 16 dB associated with an additional 40 km of fiber plusan additional 3-dB of splitting loss for increasing the split ratio from1:32 to 1:64 (1 dB spare). Also, since the Raman gain is only used tocompensate the non-flat response of the SOA, only moderate Raman pumppowers are required, resulting in a more practical, higher gain, and amore cost effective design than an all-Raman amplifier. Furthermore,since both SOAs and Raman amplifiers can be designed for any band withinthe low-loss window of optical fibers, hybrid SOA-Raman amplifiers maybe designed to meet any wavelength specifications. As such, enhancementwavelengths can be deployed by a service provider. For example, thethree enhancement wavelengths (as discussed below) are chosen tocoincide with standard CWDM channels at 1510, 1530, and 1550 nm.

Although FIG. 3 illustrates an optical extender 280 having two hybridSOA-Raman amplifiers 310 and 320, there may be scenarios where only asingle hybrid SOA-Raman amplifier is required. For example, in oneembodiment, the upstream wavelength (at 1310 nm) is amplified using aconventional SOA stage, e.g., amplifier 320 is replaced with aconventional SOA. For example, the upstream signal may not require thehybrid SOA-Raman amplifier. There may be a small power penalty (˜1 dB)due to chromatic dispersion associated with the increased transmissiondistance and added optical noise from the amplifier subsystem at thiswavelength. For example, in one embodiment, an optical filter centeredon the 1310-nm upstream channel may be included between the upstream SOAand the OLT receiver to limit the spontaneous noise added by the SOA.Note that, the downstream signals do not require additional opticalfiltering since the demultiplexer within each ONT limits the opticalbandwidth (and hence the noise bandwidth) of each channel.

For the optical extender box 280 illustrated in detail in FIG. 3, theisolators 322 and 312 are used to limit optical signals in the oppositedirection to the transmission. For example, for the downstream signalson leg or portion 310, the pump laser 315 may insert optical signal at1440 nm. The pump coupler 314 then couples the pump signal with thedownstream signals. The downstream signals are amplified as both signalspropagate in the highly non-linear fiber 313. The isolator 312 blocksthe pump wavelength from reaching the SOA 311. For the upstream leg orportion 320, the pump laser 325 inserts optical signal at 1260 nm. Thecoupler 324 couples the pump signal with the upstream signal. Theupstream signal is amplified as both signals propagate through thehighly non-linear fiber 323. The isolator 322 prevents the pump signal(1260 nm signal) from reaching the SOA 321.

In the above description, the pump wavelengths for the downstream andupstream signals were 1440 nm and 1260 nm, respectively. However, thewavelength for each pump laser may be chosen at a different nearbywavelength to optimize performance. For example, the upstream SOA 321may be chosen to have a gain peak near 1280 nm and the downstream SOA311 may be chosen to have a gain peak near 1460 nm. In addition, the SOAstage is shown as the first stage in FIG. 3. However, those skilled inthe art would realize the order of the SOA and discrete Raman stages maybe reversed depending on their relative performance.

In one embodiment, the current invention enables two or more PONs toshare a common feeder fiber by sharing an extender box. By choosingdistinct pairs of CWDM wavelengths for each PON, multiple PONs may sharea common feeder fiber. Unique pairs of standard CWDM wavelengths areused to establish downstream and upstream communication for several PONsover a common infrastructure.

In one embodiment, the bandwidth available for each ONT is increased bysubdividing a PON and using an extender box. FIG. 4 illustrates anexemplary embodiment 400 with four PONs sharing a common feeder. Indescribing the interactions of the different components in FIG. 4, thoseskilled in the art would realize that FIG. 4 may also serve as aflowchart for describing the methodology for increasing the bandwidthavailable for each ONT by allowing multiple ONTs to share a feederfiber.

For example, WDM 481 located at the central office 460 may connect aplurality of PON OLTs, e.g., the 4 PON OLTs 440-443 to the feeder fiber465. The combined signal is transmitted towards the splitter 445 throughthe optical extender box 480. The ONTs 401-432 may have wavelengthfilters in order to pass only the wavelength intended for that ONT.Members of a given sub-PON (e.g., a subgroup of ONTs 401-408, ONTs409-416, ONTs 417-424, or ONTs 425-432) would use the same opticalfilter to receive down stream information from a specific PON OLT (e.g.440, 441, 442 or 443) and also would transmit on the same upstream CWDMwavelength.

In another embodiment, the number of ONTs served by each feeder fiber isincreased by using an extender box. FIG. 5 illustrates an exemplaryembodiment 500 for multiplying the number of ONTs served by a feederfiber. In describing the interactions of the different components inFIG. 5, those skilled in the art would realize that FIG. 5 may alsoserve as a flowchart for describing the methodology for increasing thenumber of ONTs served by each feeder fiber.

For example, a 1:P WDM 582 analogous to the one used at the centraloffice is provided at a remote node 545. The WDM 582 directs thewavelength (in both directions) for each of the P passive opticalnetworks to and from a distinct passive splitter (591, 592, 593 or 594)connected to that PON's distribution fibers serving N ONTs. Each of thepassive splitters is shown serving 32 ONTs. Table 1 provides anexemplary wavelength plan for sharing the feeder fiber among 4 PONs. Thewavelengths are chosen on the CWDM grid.

TABLE 1 An exemplary wavelength plan for PONs sharing a common feederfiber. PON 1 PON 2 PON 3 PON 4 Downstream Wavelength 1 Wavelength 2Wavelength 3 Wavelength 4 wavelength 1470 nm 1490 nm 1510 nm 1530 nmUpstream Wavelength 5 Wavelength 6 Wavelength 7 Wavelength 8 wavelength1290 nm 1310 nm 1330 nm 1350 nm

In one embodiment, the current invention enables two or more PONs toshare sources for downstream wavelength services by implementing theextender box at the central office. For example, sources for downstreamservices, e.g. a high definition TV source, may be heavily shared amongseveral PONs to reduce the per subscriber cost. This embodiment permitsmore economical broadcast service by enabling the cost of the hybridSOA-Raman amplifier and laser sources to be shared among many users (viamultiple PONs).

FIG. 6 provides an exemplary network 600 with PONs heavily sharingsources. In describing the interactions of the different components inFIG. 6, those skilled in the art would realize that FIG. 6 may alsoserve as a flowchart for describing the methodology for enabling morethan one PON to share a source signal.

For example, each of the four un-cooled CWDM Distributed Feedback (DFB)laser diodes 611-614 (broadly referred to as light sources) is directlymodulated with one of the broadcast service sources 601-604 forproviding source information. The broadcast services 601-604 maycomprise of IP packets transmitted as a base-band signal (e.g. Internetprotocol based TV (IPTV)), or may comprise of digital video streamsmodulated onto radio frequency (RF) carriers, or may comprise of analogvideo signals modulated onto RF carriers, or some other electricalformat. The modulated optical signals from the four lasers 611-614 arecombined in a WDM multiplexer 620.

In one embodiment, a power combiner may be used instead of the WDMmultiplexer. The output of the multiplexer 620 is then input into ahybrid SOA-Raman amplifier 630 such that the output power issubstantially higher than the output power of each of the DFB lasertransmitters 611-614. The output of the hybrid SOA-Raman amplifier 630is input into a passive 1:M splitter 640. Each of the M outputs from thesplitter 640 having a split signal is connected to a WDM bandmultiplexer 650 a-650 m. The signal from the PON OLT for each of the Mpassive optical networks (660 a-660 m) is multiplexed with thecorresponding signal from one of the M distinct signals coming from thesplitter 640 in the appropriate multiplexer. The output of themultiplexer is then fed to a PON via a respective 670 a-670 m feeder.For example, the signal from the PON OLT 660 a is multiplexed with thecorresponding signal coming from the splitter 640 in multiplexer 650 a.The output of the multiplexer 650 a is fed to a PON via feeder 670 a.Each of the PONs being fed via 670 a-670 m may each be PONs of thecurrent invention illustrated in FIG. 2.

Thus, for a hybrid amplifier with output power of +20 dBm per channel,the splitting ratio following the amplifier might be 1:32 (typicallycorresponding to ≦17 dB splitting loss) and the excess loss of the WDMband mux may be 1 dB or less, resulting in +2 dBm launched into thefeeder fiber (which is comparable to the expected launch power perchannel in a standard PON). For the example as shown in FIG. 6, thecomponents 601-604, 611-614, 620, 630 and 640 may comprise a sharedtransmitter 645 and may serve 32×32=1024 users. It has been observedthat using the shared transmitter 645 will significantly lower the costper PON when compared to conventional transmitters.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of a preferred embodiment shouldnot be limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the following claims and theirequivalents.

1. An optical network, comprising: a plurality of optical linetermination devices, where each optical line termination device having atransceiver for sending a first optical signal at a first wavelength andreceiving a second optical signal at a second wavelength, wherein thefirst wavelength and the second wavelength are different; a wavelengthdivision multiplexer combiner, coupled to the plurality of optical linetermination devices, for combining optical signals received from theplurality of optical line termination devices; an optical extender boxcomprising a first wavelength diplexer and a second wavelength diplexer,wherein the first wavelength diplexer and the second wavelength diplexerare both coupled to a first portion and a second portion, wherein thefirst portion is for transporting the first optical signal at the firstwavelength and the second portion is for transporting the second opticalsignal at the second wavelength, wherein the first portion in anupstream direction comprises an upstream semiconductor amplifier, whichis connected to an upstream isolator, which is connected to an upstreamnon-linear fiber, which is connected to an upstream pump laser, whereinthe second portion in a downstream direction comprises a downstreamsemiconductor amplifier, which is connected to a downstream isolator,which is connected to a downstream non-linear fiber, which is connectedto a downstream pump laser, wherein the optical extender box amplifiesdownstream time division multiplexing wavelengths and downstream coarsewavelength division multiplexing wavelengths, wherein the opticalextender box is coupled to the wavelength division multiplexer combinervia a first single mode fiber section; and an optical splitter coupledto the optical extender box via a second single mode fiber section. 2.The optical network of claim 1, wherein the optical splitter is apassive optical splitter.
 3. The optical network of claim 1, wherein theoptical extender box extends a sum of the first single mode fibersection and the second single mode fiber section to be greater than 20km.
 4. The optical network of claim 3, wherein the optical extender boxextends the sum of the first single mode fiber section and the secondsingle mode fiber section to be within a range of 20 km to 60 km.
 5. Theoptical network of claim 1, wherein the plurality of optical linetermination devices and the wavelength division multiplexer combiner aredeployed in a single central office.
 6. The optical network of claim 1,wherein the optical splitter is coupled to a plurality of opticalnetwork termination devices.
 7. The optical network of claim 6, whereinthe plurality of optical network termination devices is organized into aplurality of subgroups, where each subgroup of optical networktermination devices employs filtering to only receive down streaminformation from one of the plurality of optical line terminationdevices.
 8. The optical network of claim 1, wherein each of theplurality of optical line termination devices having a downstreamtransmission wavelength of 1470 nm-1530 nm.
 9. The optical network ofclaim 1, further comprising: a wavelength division multiplexer splitter,coupled between the optical extender box and the optical splitter, forseparating the combined optical signals received from the opticalextender box.
 10. The optical network of claim 9, wherein the opticalsplitter comprises a plurality of optical splitters.
 11. The opticalnetwork of claim 10, wherein each of the plurality of optical splittersis coupled to a plurality of optical network termination devices. 12.The optical network of claim 10, wherein each of the plurality ofoptical splitters has a splitting ratio of 1:32.
 13. An optical network,comprising: a plurality of optical line termination means, where eachoptical line termination means having a transceiver for sending a firstoptical signal at a first wavelength and receiving a second opticalsignal at a second wavelength, wherein the first wavelength and thesecond wavelength are different; a wavelength division multiplexercombining means, coupled to the plurality of optical line terminationmeans, for combining optical signals received from the plurality ofoptical line termination means; an optical extender box means comprisinga first wavelength diplexer and a second wavelength diplexer, whereinthe first wavelength diplexer and the second wavelength diplexer areboth coupled to a first portion and a second portion, wherein the firstportion is for transporting the first optical signal at the firstwavelength and the second portion is for transporting the second opticalsignal at the second wavelength, wherein the first portion in anupstream direction comprises an upstream semiconductor amplifier, whichis connected to an upstream isolator, which is connected to an upstreamnon-linear fiber, which is connected to an upstream pump laser, whereinthe second portion in a downstream direction comprises a downstreamsemiconductor amplifier, which is connected to a downstream isolator,which is connected to a downstream non-linear fiber, which is connectedto a downstream pump laser, wherein the optical extender box meansamplifies downstream time division multiplexing wavelengths anddownstream coarse wavelength division multiplexing wavelengths, whereinthe optical extender box means is coupled to the wavelength divisionmultiplexer combining means via a first single mode fiber section; andan optical splitting means coupled to the optical extending means via asecond single mode fiber section.
 14. The optical network of claim 13,wherein the optical splitting means is a passive optical splitter. 15.The optical network of claim 13, wherein the plurality of optical linetermination means and the wavelength division multiplexer combiningmeans are deployed in a single central office.
 16. The optical networkof claim 13, wherein the optical splitting means is coupled to aplurality of optical network terminating means.
 17. The optical networkof claim 16, wherein the plurality of optical network termination meansis organized into a plurality of subgroups, where each subgroup ofoptical network termination means employs filtering to only receive downstream information from one of the plurality of optical line terminationmeans.
 18. The optical network of claim 13, wherein each of theplurality of optical line termination means having a downstreamtransmission wavelength of 1470 nm-1530 nm.
 19. The optical network ofclaim 13, further comprising: a wavelength division multiplexersplitting means, coupled between the optical extending means and theoptical splitting means, for separating the combined optical signalsreceived from the optical extending means.
 20. A method for providing anoptical network, comprising: providing a plurality of optical linetermination devices, where each optical line termination device having atransceiver for sending a first optical signal at a first wavelength andreceiving a second optical signal at a second wavelength, wherein thefirst wavelength and the second wavelength are different; providing awavelength division multiplexer combiner, coupled to the plurality ofoptical line termination devices, for combining optical signals receivedfrom the plurality of optical line termination devices; providing anoptical extender box comprising a first wavelength diplexer and a secondwavelength diplexer, wherein the first wavelength diplexer and thesecond wavelength diplexer are both coupled to a first portion and asecond portion, wherein the first portion is for transporting the firstoptical signal at the first wavelength and the second portion is fortransporting the second optical signal at the second wavelength, whereinthe first portion in an upstream direction comprises an upstreamsemiconductor amplifier, which is connected to an upstream isolator,which is connected to an upstream non-linear fiber, which is connectedto an upstream pump laser, wherein the second portion in a downstreamdirection comprises a downstream semiconductor amplifier, which isconnected to a downstream isolator, which is connected to a downstreamnon-linear fiber, which is connected to a downstream pump laser, whereinthe optical extender box amplifies downstream time division multiplexingwavelengths and downstream coarse wavelength division multiplexingwavelengths, wherein the optical extender box is coupled to thewavelength division multiplexer combiner via a first single mode fibersection; and providing an optical splitter coupled to the opticalextender box via a second single mode fiber section.